在室外游泳英文是"outdoor swimming"。
"Outdoor"是形容词，指"在户外的，户外的"，来自英文"out"，意思是"在外面"，和"door"，意思是"门"，因此"outdoor"的意思就是"在户外的"。
"Swimming"是名词，指"游泳"，来自英文"swim"，意思是"游泳"。
例句：
I love outdoor swimming in the summer. (我喜欢夏天在室外游泳。)
The outdoor swimming pool is heated. (户外游泳池加热了。)
Can you teach me outdoor swimming techniques? (你能教我在室外游泳的技巧吗？)